February's Focal Point: smart infrastructures

High and extra high voltage transmission networks

Europe’s meshed alternating current (AC) grid network has reached its current limits and requires short-term upgrading. AC overhead line technology has been and will remain the main technology for high and extrahigh AC voltage transmission lines (220 – 400 kV). That said, in sensitive areas, partial undergrounding may be applied to address local concerns.

In addition, Europe is setting is setting out to create a High Voltage Direct Current (HVDC) grid structure to transport high power loads over long distances with minimal losses. HVDC overhead technology is compatible with HVDC underground cables. Meshed grids / networks will require the use of DC circuit breakers with high power breaking capacity.

A hybrid transmission system consisting of HVAC 400 kV+ and HVDC overlay network will require state-of-theart
patterns of operation, monitoring and interoperability including converter stations. Concrete recommendations – transmission networks:

• RD&D is to take a two-stage approach, the first stage dealing with short and medium-term achievable targets and a second stage targeting the longer-term.
• As foreseen by the Commission’s Infrastructure Guidelines, permitting procedures are to be streamlined, financing is to be secured and public acceptance is to be addressed from the outset of project consideration.
• Deployment of new technologies is to be enabled including:
    ° Integration of partial undergrounding in upgrading of 400kV grid.
    ° Complementing 400kV grid with additional HVDC overlay grid via DC breakers and converter stations.
• Lighthouse projects should be identified for the deployment of new technologies in a larger framework.

Smart low-to-medium voltage distribution networks

With more and more renewable energy sources coming on stream, an increasingly decentralised electricity grid will be needed to allow active power distribution. Power distribution is more obviously, though by no means exclusively, impacted by the changes implicit in the basket of developments often referred to as the “smart grid”. Concrete recommendations – distribution networks:

• Distribution system operators (DSOs) need to gain more experience and be supported for R&D spending
in this field by appropriate regulation.
• System operations in distribution will have to evolve to a new standard in reliability as well as functionality to
ensure proper reliability of supply.
• The current approach, using only cost-analyses to assess risk, penalises the highly technological changes that are required, for instance, to integrate small-to-medium sized renewable energy sources. Recommendations from the EEGI (European Energy Grid Initiative) will speed up the knowledge-sharing process among the different DSOs. For mid-to-long term objectives, what is actually indicated in the SRA 2007 should be applied.